do_checks' stk_expr hp_expr stk_nonzero hp_nonzero reg_save_code rts_lbl
= do { doGranAllocate hp_expr
- -- Emit a block for the heap-check-failure code
- ; blk_id <- forkLabelledCode $ do
- { whenC hp_nonzero $
- stmtC (CmmAssign (CmmGlobal HpAlloc) hp_expr)
+ -- The failure block: this saves the registers and jumps to
+ -- the appropriate RTS stub.
+ ; exit_blk_id <- forkLabelledCode $ do {
; emitStmts reg_save_code
; stmtC (CmmJump rts_lbl []) }
+ -- In the case of a heap-check failure, we must also set
+ -- HpAlloc. NB. HpAlloc is *only* set if Hp has been
+ -- incremented by the heap check, it must not be set in the
+ -- event that a stack check failed, because the RTS stub will
+ -- retreat Hp by HpAlloc.
+ ; hp_blk_id <- if hp_nonzero
+ then forkLabelledCode $ do
+ stmtC (CmmAssign (CmmGlobal HpAlloc) hp_expr)
+ stmtC (CmmBranch exit_blk_id)
+ else return exit_blk_id
+
-- Check for stack overflow *FIRST*; otherwise
-- we might bumping Hp and then failing stack oflo
; whenC stk_nonzero
- (stmtC (CmmCondBranch stk_oflo blk_id))
+ (stmtC (CmmCondBranch stk_oflo exit_blk_id))
; whenC hp_nonzero
(stmtsC [CmmAssign hpReg
(cmmOffsetExprB (CmmReg hpReg) hp_expr),
- CmmCondBranch hp_oflo blk_id])
+ CmmCondBranch hp_oflo hp_blk_id])
-- Bump heap pointer, and test for heap exhaustion
-- Note that we don't move the heap pointer unless the
-- stack check succeeds. Otherwise we might end up